Power generation complex plant and plant control method

Abstract

A power generation complex plant has a control switch, an overall control unit and a steam bypass facility. The overall control unit determines that a desired steam volume has reached a limit value of the volume of steam to be generated by a steam generating facility. A steam bypass facility control unit adds a bias value B 1 to a control command value V 4 of the steam bypass facility to generate a new control command value V 5 when the desired steam volume is determined to have reached the limit value. The steam bypass facility control unit then controls the volume and pressure of steam passing through the steam bypass facility on the basis of the new control command value V 5 so that no switch of control may be made in the control switch.

1. A power generation complex plant comprising:
 a steam generating facility; 
 a high-pressure steam header into which steam generated in the steam generating facility is supplied; 
 a steam power generating facility which generates electricity by use of the steam supplied from the high-pressure steam header; 
 a low-pressure steam header into which the steam flowing out of the steam power generating facility is supplied; 
 a steam bypass facility which links the high-pressure steam header to the low-pressure steam header in such a manner as to bypass the steam power generating facility and which adjusts the volume, pressure, and temperature of the steam supplied from the high-pressure steam header on the basis of a bypass steam volume control command value and then supplies the steam to the low-pressure steam header; 
 a steam consuming facility which uses the steam supplied from the low-pressure steam header; 
 a low-pressure control unit which controls the volume of steam to be supplied to the steam power generating facility on the basis of the steam pressure in the low-pressure steam header when the steam pressure in the high-pressure steam header is higher than a preset threshold value; 
 a high-pressure control unit which controls the volume of steam to be supplied to the steam power generating facility on the basis of the steam pressure in the high-pressure steam header when the steam pressure in the high-pressure steam header is lower than a preset threshold value; 
 a control switch unit which compares the steam pressure in the high-pressure steam header with the threshold value to switch between control by the low-pressure control unit and control by the high-pressure control unit; 
 a determining unit which determines that a desired steam volume of the steam consuming facility has reached an upper limit value of the volume of steam to be generated by the steam generating facility; and 
 a steam bypass facility control unit which adds programmed to add a bias value to the bypass steam volume control command value of the steam bypass facility to generate a new bypass steam volume control command value when the determining unit determines that the desired steam volume has reached the upper limit value, in order to control the volume and pressure of the steam passing through the steam bypass facility on the basis of the new bypass steam volume control command value. 
 
     
     
       2. The power generation complex plant according to  claim 1 , wherein
 the determining unit determines the upper limit value in accordance with the steam pressure in the high-pressure steam header. 
 
     
     
       3. The power generation complex plant according to  claim 1 , wherein
 the determining unit determines the upper limit value in accordance with a control command value for the steam generating facility. 
 
     
     
       4. The power generation complex plant according to  claim 1 , wherein
 steam generated by another steam generating facility is also supplied into the high-pressure steam header, 
 the power generation complex plant further comprising a steam generating facility control unit which adds a bias value to a steam generation volume control command value for the other steam generating facility to generate a new control command value when the determining unit determines that the desired steam volume has reached an upper limit value of the generated steam volume, in order to control the volume of steam to be generated by the other steam generating facility on the basis of the new control command value. 
 
     
     
       5. The power generation complex plant according to  claim 4 , further comprising:
 a priority order selecting unit which selects either control by the steam generating facility control unit or control by the steam bypass facility control unit on the basis of a preset priority order when the determining unit determines that the desired steam volume of the steam consuming facility has reached an upper limit value of the generated steam volume. 
 
     
     
       6. The power generation complex plant according to  claim 5 , wherein
 the priority order selecting unit includes a unit which determines a priority order on the basis of power generation efficiency of the whole power generation complex plant. 
 
     
     
       7. The power generation complex plant according to  claim 1 , further comprising:
 a bias value calculation unit which calculates the bias value from the steam pressure in the high-pressure steam header. 
 
     
     
       8. The power generation complex plant according to  claim 1 , wherein
 the steam consuming facility is a desalination facility which consumes the steam supplied from the low-pressure steam header to generate product water. 
 
     
     
       9. The power generation complex plant according to  claim 1 , wherein
 the steam generating facility is an exhaust heat recovery boiler which includes a duct burner and which uses an exhaust gas of a gas turbine as a heat source to generate steam. 
 
     
     
       10. A plant control method for use in a power generation complex plant, the power generation complex plant including:
 a steam generating facility; 
 a high-pressure steam header into which steam generated in the steam generating facility is supplied; 
 a steam power generation facility which generates electricity by use of the steam supplied from the high-pressure steam header; 
 a low-pressure steam header into which the steam flowing out of the steam power generating facility is supplied; 
 a steam bypass facility which links the high-pressure steam header to the low-pressure steam header in such a manner as to bypass the steam power generating facility and which adjusts the volume, pressure, and temperature of the steam supplied from the high-pressure steam header on the basis of a bypass steam volume control command value and then supplies the steam to the low-pressure steam header; 
 a steam consuming facility which uses the steam supplied from the low-pressure steam header; 
 a low-pressure control unit which controls the volume of steam to be supplied to the steam power generating facility on the basis of the steam pressure in the low-pressure steam header when the steam pressure in the high-pressure steam header is higher than a preset threshold value; 
 a high-pressure control unit which controls the volume of steam to be supplied to the steam power generating facility on the basis of the steam pressure in the high-pressure steam header when the steam pressure in the high-pressure steam header is lower than a preset threshold value; and 
 a control switch unit which compares the steam pressure in the high-pressure steam header with the threshold value to switch between control by the low-pressure control unit and control by the high-pressure control unit, 
 the plant control method comprising: 
 a determining step of determining that a desired steam volume of the steam consuming facility has reached an upper limit value of the volume of steam to be generated by the steam generating facility; and 
 a steam bypass facility control step of adding a bias value to the bypass steam volume control command value of the steam bypass facility to generate a new bypass steam volume control command value when the determining step determines that the desired steam volume has reached the upper limit value, in order to control the volume and pressure of the steam passing through the steam bypass facility on the basis of the new bypass steam volume control command value. 
 
     
     
       11. The plant control method according to  claim 10 , further comprising:
 a steam generating facility control step of adding a bias value to a control command value for another steam generating facility to generate a new control command value when the determining step determines that the desired steam volume has reached an upper limit value of the generated steam volume, in order to control the volume of steam to be generated by the other steam generating facility on the basis of the new control command value. 
 
     
     
       12. The plant control method according to  claim 11 , further comprising:
 a priority order selecting step of selecting either control by the steam generating facility control step or control by the steam bypass facility control step on the basis of a preset priority order when the determining step determines that the desired steam volume has reached an upper limit value.